Method for making jet tubes



Filed March 2, 1953 June 30, 1959 H. A. HUTCHINS ETAL 2,892,253

METHOD FOR MAKING JET TUBES 2 Sheets-Sheet 1 i o o o p/ \0 a 4 5'0 1 616'0 66 a! 41 40 40 4 34 s I HUGH A. HUTCH/N5,

,eucs C. (IO/v55, B 4 a 2 5 fll WM 6083 B A i i am e y.

June 30, 1959 H. A. HUTCHINS ETAL 2,892,253

METHOD FOR MAKING JET TUBES Filed March 2, 1953 2 Sheets-Sheet 2lllllLil j nvenzors.

Huey A. HJTCH/NS, BRUCE C. rib/v55,

U ited States Patent 2,892,253 lVIETHOD FORMAKING JET TUBES Hugh A.Hutchins, Arcadia, and Bruce C. Jones, Monrovia, Calif. ApplicationMarch 2, 195$,Serial No. 339,638

7 v v 6 Claims. (Cl. 29-421) This invention has to do with a method forthe making ,of jet tubes, thatis, forthe making of tubular units for thehandling offluids at high pressure and temperatures, ,as for, instance,units for use in jet motors or propelling apparatus.

The tubes or nozzle-like elements. employed in jet en- .gines, and thelike, are, in the nature of venturi tubes, and they operate under severeconditions both as topressure and as to temperature. The handling anddistribution of heat;incidental. tothe operation of units of thischaracter presents a diflicult problem and such a unit must be ofuniform flawless construction, as otherwiseit is likelyttonfail and mayresult in serious damage inthe event of failure.

It is a general object of this invention to provide a .method whereby ajet tubein thegeneral nature of a venturi tube can be formed to. have afluted or corrugated .liner within a smooth-walled jacket, and in whichthe construction isfree of joints or seams that are likely to fail.

It is another object of this invention to provide a method by whichsimple, straight, metallic tubes, preferably seamless metal tubes, arecombined into a unit wherein the tubes are bonded together and by whichcorrugations are established in the innertube by the application offluid pressure thereto.

It is another object of this invention to provide a .method of thegeneral character referredto, by which a smooth-walled outer-tube orjacket is combined with an inner tube or-linerhaving corrugations formedbyfluid pressure, sothat the'tubes are in uniform continuouscontactt-hroughoutthe length ofthe structure and are bonded ltogetherwhere they are in contact with each other, thus -.providing a structurethat is highly eflicient and effective 1 for the j general purposeintended, which is eifective and .Walled' jacket, ,with a liner, andfor'the formation ofcorrugationsinithe liner by the application of.fluidpressure.

:ln {the following detailed description, reference :is made to a typicalapparatus-for carryingout the methodofthe present invention.

Eig. 1 isa sideelevation of-a typical tubularpartthat I will bereferredto asaliner stock, and attherighthand end thereof this elementisindicated by dotted lines .in the flared condition, resulting from thefirst .operation performed thereon. ;Fig. 2 is'aview illustratingitheliner ,stoek partially formed, that is, having its :large end por- .li:il? l 1 h vin a inte m di t portion re u e rtwfi h i ne k .as sp nin oer mand el o p determ inedvsize and shape. -Eig. 3 is a view similar ;to"1, showing the element of the structure that forms the casevor jacketof the finished unit, being a view of thejacket stockcorresponding toFig. 1 which illustrates thelliner stock. Fig; 4 isla view similar toFig. 2, showin the nd l u t at itals 2 .li PhP dbY a manf ir p ded b thrre s lt ri smi a an s owi th ia st ed es 9 h s mme -9 ormed ov o sa s.th

liner stock. Fig. 5 is a detailed transverse sectional view ice.longitudinal sectional view of apparatus employed ill].

carrying out the invention, showing the mandrel. and the elementsthereon as illustrated inFig. 4 located inapressure chamber or chestandindicating the presence of pressure which serves tofornithecorrugationsin the liner stock. Fig. 7 is a detailed transversesectional view of a structure that maybe employed in the course ,ofbonding the jacket .and liner together at the. conclusion of theprocess, and Fig. 8 is a view of the finished tube or unit, with theparts broken away to illustrate details of construction.

The method as provided" by the present inventionis particularly usefulandpractical'for the formation of a jet tube orrventuri type duct asshown in Fig. 7 oft-he drawings, which unit is characterized by asmooth-walled jacket .10 and a corrugated liner 11 within the-jacket,which parts are in bearing engagernent with each other (from one endportion to the other of the unit and are preferably bondedtogether wherethey contact, the unit being an elongate tubular element in the natureof a verituri tube. The unit is characterized by end portions connectedby an intermediate or neckportion ofreduced diameter, and it may, inpractice, he provided at itsends with fittings or accessories asillustrated inFig. 8 of the drawings.

In accordance withthe broader-principlesof the present invention, asmooth-walled jacket is formed primarily by means of spinning, whereasthe fluted or corrugated liner is formed preferably by spinningandthe-application of fluid pressure in the courseof which the liner isrelated to a formingrnernber having longitudinal grooves pr flutestherein, and to which the liner is shaped to give-it the desired flutedor corrugated-form. Inthe particular form of the invention illustratedin the drawings, and

which-is to;be referredto in detail, the member,wi th which the liner isrelated asfluid pressure'is applied in the course of formingthefcorrugations, is'located within the-liner and is in thenature of amandrel and, ingthis case, after thejacket-has been, established overtheliner,

theliner is corrugated or fluted, leavingthejjacket and liner with partsin contact ready for .thefinishin jQPQration or bonding.

In the particular case .illustrated in the -drawings, a simple, straightlength of tubing, preferably seamless metal tubing, suchas is shown inFig. .1 of th'edrawings isprovidedas the liner stock, and in accordancewiththe firstloperation, this liner stock is flared orbellediatone n f na w hap uc a is ind ca i ii d tte l e at h qr eht n' is- Th be n flarino the liner stock may, in practice, he carried out by any suitableforming or working of the metal of theliner stock, it being preferredordinarily that this operation. beperformed by spinning.

Following flaring ofthe liner stock atone end a mandrel A is inserted inthe liner stockandhas an end portion 1-2 which is straight and round andwhich snugly or slidablyfits into the end portion :13 ofthe liner stock.

The other end portion 14 of themandrelA is 'flared as shown in Fig. 2and-the end portions 12 and 14 are conneeted by a reduced portion orneck 15, where the mandrel is divided or-split as at 16 so that it issectional.

A suitable means is provided for holdingthe mandrel sections togetherand, in the case illustrated, thisineans is shown as including a rod 17extending longitudinally through the mandrel sections centrally thereofand the rod has ahead 18 at one end and has a nut .19 threaded ontoitatthe other end. When them1t19is made tight, the liner sections aretightly .clamped together. The mandrel A with the flared liner stockthereon, as indisuch as a lathe ready for spinning. In the caseillustrated, the assembly is carried between centers 20, and a drive dog21 carried by a rotating head 22 is engaged with the assembly to driveit.

As the assembled flared liner stock and mandrel A are rotated as a unit,a suitable forming or spinning tool 25 is employed to spin the flaredend portion of the liner stock onto the flared or tapered end 14 of themandrel, and the liner stock is spun inward at the neck portion 15 toform the liner stock with a reduced portion or neck 26 as clearlyillustrated in full lines in Fig. 2.

In accordance with the present invention, it is contemplated that theliner stock may be a seamless tube of a suitable metal or alloy, forinstance, in practice, it may be steel. To facilitate and expedite thedesired working of the liner stock, it is preferred to anneal it,following the spinning as hereinabove described to render it soft andready for fluting or corrugating as hereinafter described. If desired ornecessary, the liner stock may be annealed in the course of spinning itinto the desired form and if desired or necessary, the mandrel A may betemporarily removed to facilitate or expedite proper annealmg.

The element which is to form the jacket is initially a simple, straight,elongate, tubular part, this element or jacket stock being illustratedin Fig. 3, where the initial form is indicated in dotted lines. It iscontemplated that the jacket stock be a seamless tube of suitable metalor alloy, for instance, in practice, it may be steel.

The jacket stock as shown in Fig. 3 is there illustrated after theinitial belling operation has been performedas by spinning to establishthe stock flared at one end as at the right hand end. The flared end Xof the jacket stock is preferably formed to correspond in taper or flarewith the flared end of the liner stock.

Following the flaring of the jacket stock to establish this element inthe form shown in Fig. 3, the jacket stock is applied to the flared andspun liner stock carried on mandrel A while the mandrel A is maintainedwithin the liner stock. The assembled liner stock and jacket stockcarried on mandrel A are then placed in a lathe, or the like, and aspinning operation is performed on the jacket stock the same as thatwhich was performed on the liner stock, to the end that the jacket stockhas a neck portion 67 formed or spun in to fit close around and over theneck portion 26 of the liner stock, and has end portions 68 and 69fitting snugly around the end portions 13 and 33 respectively, of theliner 11. The manner in which the liner stock and jacket stock fittogether at the conclusion of this operation is clearly illustrated inFig. 4 of the drawings.

When the jacket has been formed over or established on the spun linerstock so that these parts correspond to the shape of the mandrel A, thesections of mandrel A are released as by removal of nut 19, and themandrel A is removed from the liner stock as by separating the parts.

The assembled jacket stock and liner stock, after being free of mandrelA, have a mandrel B applied thereto. Mandrel B is, like mandrel A,sectional and such that it can be assembled into the liner stock fromthe ends thereof. The mandrel B as shown in Fig. 4 of the drawings hasan end portion 30 fitting into the long straight end portion 13 of theliner stock, and it has a flared end portion 31 fitting into the flaredend portion 33 of the liner stock. The mandrel B has a reduced portionor neck 34 fitting snugly into the portion 26 of the liner stock and themandrel B is split at 35 so that it is sectional as shown in Fig. 4 ofthe drawings.

In accordance with the present invention, the exterior of the mandrel B,instead of being smooth and plain as is the exterior of mandrel A, isgrooved or fluted, being preferably uniformly grooved or fluted from oneend to the other, as by like parallel grooves 40 which join at ribs orcrests 41.

The sections of the fluted mandrel B are releasably secured or tiedtogether as by a rod 60 having a head 61 at one end and a nut 62threaded on it at the other end. The interior of the mandrel B withinthe grooved portion thereof is recessed as at 80, establishing an openchamber 83 in the mandrel around the rod 60. Bleed holes 81 extend fromthe bottom of grooves 40 to the chamber 83.

It is preferred that the jacket stock be shorter than the liner stock,so that parts of the liner stock project beyond the terminal ends of thejacket stock and the grooves 40 in mandrel B are of such length and areso located as to extend beyond the tenninal ends of the jacket stock andterminate within said parts of the liner stock and before reaching theterminal ends of the liner stock (see Figs. 4 and 6).

The assembly formed by the initially formed liner stock, the jacketthereon, and the mandrel B is arranged in a chest C, or the like, whichis closed and which establishes a pressure chamber 43. In the particularcase illustrated, the chest C has a tubular or cylindrical body 44closed at its ends by headers 45 and the assembly including the mandrelB is arranged in the body 44 and is held tight between the headers 45with the ends of the liner stock sealed with the headers as by seals 46or other suitable means.

A fluid handling duct 47 is provided to supply fluid under pressure,preferably liquid, into the body 44 around the assembly located therein,and a valve controlled pressure relief connection 48 is provided so thatair can be exhausted from the chest as desired. A drain connection 49 isshown at the bottom of the chest.

With the parts assembled as illustrated in Fig. 6 fluid under pressure,say, for instance, oil or water under a substantial pressure, is appliedto chest C, and acts to collapse or form the liner stock inwardly sothat it becomes grooved or fluted to be, in effect, corrugated. It willbe apparent that by applying a suitable pressure to the exterior of theliner stock, it is forced in, onto, or against the mandrel B so that ittakes on the exact shape or contour of the exterior of mandrel B. It isto be understood, of course, that, in practice, the sections of mandrelB are keyed together as by one or more pins 50, or the like, so that theflutes or grooves in the sections of mandrel B are aligned so that theliner stock is pressureformed to have uniform continuous corrugationsformed in it extending continuously lengthwise of it from one end to theother. As the pressure forming operation is carried out, the air ingrooves is exhausted through the holes 81 and into the chambersoccurring in the mandrel B.

At the conclusion of the pressure forming operation, the mandrel B isremoved, leaving the liner stock and jacket stock both in finished formand assembled as shown in Fig. 8 of the drawings, where these parts areshown provided with suitable fittings or accessories. For some purposesthis assembly may be adequate; however, it is preferred for most usesthat the liner and jacket stocks be bonded together where they contactor are in engagement with each other. It is therefore preferred incarrying out the invention that a bonding operation be performed, forinstance a suitable flux, bonding agent, or possibly a coating can beapplied to either one or both of the stocks prior to the stepshereinabove set forth, or after the structure has been assembled asshown in Fig. 8 and with suitable materials present or conditionsprevailing, heat may be applied to effect the desired bonding of thestocks. In Fig. 7 there is illustrated in a somewhat diagrammatic mannerthe assembled stocks in a heating venturi tube, or the like, and whereinthe inner tube is continuously and uniformly corrugated from one endportion of the structure to the other. By employing the presentinvention, a jet tube as shown in Fig. 8 is provided having uniformseamless structural character, except insofar as the liner and jacketare engaged and there joined, and it will be apparent that the structureresulting from the invention presents a maximum surface for exposure tofluid handled by the structure, and an efficient and effectiveconstruction for the transfer of heat from the inside to the outside ofthe structure without resulting in hot spots and all without any weakpoints or parts likely to become over-stressed or subject to weakeningor failure. As the structure is used, a suitable fluid may be handled bythe fittings at the ends thereof, so as to be circulated through theduct-like passages 90 that are established between the liner and jacketas shown in the drawings.

Having described only a typical preferred form of apparatus and atypical manner of carrying out the method of our invention, we do notwish to be limited or restricted to the specific details herein setforth, but wish to reserve to ourselves any variations or modificationsthat may appear to those skilled in the art and fall within the scope ofthe following claims.

Having described our invention, we claim:

1. The method of fabricating a jet tube of the character referred towhich includes, spinning a neck portion of reduced diameter in a firstinner tube intermediate the ends thereof, arranging the formed innertube within and in telescopic relation with a second outer tube, thenspinning a reduced neck portion in the outer tube corresponding to theneck portion of the inner tube and in contact therewith, arranging alongitudinally inwardly fluted member within the inner tube, sealing theend of inner tube with the said member and then applying fluid pressureto the exterior of the inner tube to urge said inner tube intoconformity with said member and forming inwardly projecting groovestherein longitudinally thereof and throughout the neck portion thereof.

2. The method of fabricating a jet tube of the character referred towhich includes, flaring a straight round first inner tube at one endthereof, inserting sections of a plain round mandrel having a reducedintermediate portion in the inner tube to abut therein where the mandrelis of reduced diameter, spinning the said inner tube into the reducedportion of the mandrel to form a neck portion intermediate the endsthereof, then applying a flared second outer tube over the inner tubeand spinning the outer tube to establish the outer tube in contact withthe outermost parts of the first menioned tube, replacing the said plainmandrel with a sectional mandrel having an inwardly fluted exterior,then sealing the ends of the inner tube with the fluted mandrel and thenapplying fluid pressure to the exterior of the inner tube only wherebythe inner tube is formed to conform to the shape of the fluted mandrel,then removing the sections of the fluted mandrel and then bonding thetubes together where they are left in contact with each other.

3. The method of fabricating a jet tube of the character referred towhich includes, forming a first inner tube with a neck portion ofreduced diameter intermediate the ends thereof, arranging the formedinner tube within and in telescopic relation with a second outer tube,then forming the outer tube with a neck portion corresponding to theneck portion of the inner tube and in contact therewith, arranging aninwardly fluted member adjacent the inner wall of the inner tube, thensealing the ends of said inner tube with said fluted member, and thenapplying fluid pressure to the exterior of the inner tube to urge thesaid inner tube into conformity with the said member and to formlongitudinal inwardly projecting grooves therein which grooves establishlongitudinal passageways between the tubes and so the inner tube haslongitudinal ridges that are in contact with the outer tube, and thenremoving said member from the inner tube.

4. The method of fabricating a jet tube of the character referred towhich includes forming a first inner tube with a neck portion of reduceddiameter intermediate the ends thereof, arranging a second outer tubeover the inner tube and forming it with a neck portion engaged aroundthe neck portion of the outer tube, inserting sections of alongitudinally inwardly fluted member in the inner tube from oppositeends thereof and to abut within the reduced neck portion thereof,sealing the end of the inner tube with the said member, then applyingfluid pressure to the exterior of the first tube only to urge it intoconformity with the said member and establish longitudinal groovestherein and then removing the said member.

5. The method of fabricating a jet tube of the character referred towhich includes forming a first inner tube with a neck portion of reduceddiameter intermediate the ends thereof, then arranging a second outertube over the first tube and forming it to engage the inner tubesubstantially continuously throughout the longitudinal extent thereof,inserting sections of a longitudinally inwardly fluted member in theinner tube from opposite ends thereof and to abut within the neckportion thereof, sealing the end of the inner tube with the said member,then applying fluid pressure to the exterior of said inner tube only tourge it into conformity with the said member and establish longitudinalgrooves therein, then removing the member from the inner tube and thenbonding the tubes together where they are engaged with each other.

6. The method of fabricating a jet tube of the character referred towhich includes forming a first inner tube with a neck portion of reduceddiameter intermediate the ends thereof, then arranging a second outertube over the inner tube and forming it to engage the inner tubesubstantially continuously throughout the 1ongitudinal extent thereof,inserting sections of a longitudinally inwardly fluted member in theinner tube from opposite ends thereof and to abut within the neckportion thereof, sealing the end of the inner tube with the said member,then applying fluid pressure to the exterior of said first tube only tourge it into conformity with the said member and establish longitudinalgrooves therein, then removing the member from the inner tube and thenapplying heat to the tubes to effect bonding of the tubes together wherethey are engaged with each other.

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